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The Wind-Tunnel PC

Pick your fan

I picked a 120mm mains fan for this project, primarily because I got a dozen of them for four bucks each from Overclocker's Paradise here in Malaysia.

If you choose a mains powered fan for your computer, do NOT attempt to install it yourself if you are not experienced at working with mains powered apparatus. Even if you manage to get it to work, you may wire it unsafely and kill or injure someone later on. 12 volt fans are safe to work with; the worst injury they can inflict is a bruised fingernail, and the worst mistake you can make will probably just pop a fuse in your power supply. But mains electricity is not to be trifled with.

When choosing your fan, bear in mind that the amount of air a fan moves varies markedly with its size. Roughly speaking, the airflow of similarly shaped fans varies with the square of the fan diameter, so a fan double the size moves something like four times as much air. Often more, in fact, because the motor assembly in a larger fan is smaller in comparison to the blade length. Mains powered fans have much larger motor assemblies, which in 80mm mains fans leave precious little room for the blades. The mains motors are much more powerful, though, so 120mm and 150mm mains fans can move far more air than a 12 volt model with low enough current consumption to run in a PC without overtaxing the computer's PSU. A 120mm fan is more than adequate for even the hottest games box; it moves roughly three times as much air as the average 80mm PSU fan.